The thumb2 decoder contained a mixup between the bit controlling
doubling and the bit controlling if the operation was an add or a sub.
Signed-off-by: Johan Bengtsson <teofrastius@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Nathan Froyd <froydnj@codesourcery.com>